Tap the sliders icon at the top of your list to open List settings, where you rename it, change who can see it or who can reserve, or delete it.
The ⋯ menu on the list's card in Wishes → Lists has Settings too. If the sliders icon is greyed out with "You're not allowed to edit this wishlist", your access doesn't include settings: see "What can each access level do?".
Steps
Open your list and tap the sliders icon at the top: on a computer it's next to Share, on a phone next to the share icon.
Tap the row you want. On a phone it opens on its own screen.
Make your change. There's no Save button: you'll see "Saved" straight away, with Undo after a name or description change.
What can I change in List settings?
Everything about the list except its wishes:
Rename it, add a description or set the cover in Name and description.
Choose who can open it in Who can see it (more in "Who can see my wishlist?").
Invite people to help in People with access (more in "How do I invite someone to edit my list?").
Choose whether friends must sign in to reserve in Who can reserve (more in "Can I see what's reserved on my list?").
Set the Occasion, Date and Who's it for? in What this list is for; the occasion and who it's for shape the list's gift ideas. Clear date removes the date.
On the list page, you can also tap the name, description or date to change them. A list with an occasion but no date shows Add a date under its name.
How do I add a cover photo to my list?
Tap Add a cover next to the list's name, then pick a photo and frame it.
Tap Add a cover, or find it under Cover image in Name and description.
In My photo, tap Upload an image and choose a photo up to 5 MB. Or open Find a photo, search for one and tap it.
Drag it to choose what shows, then tap Save position.
The cover runs across the top of the list and is the picture on its card. A bigger file gets "File is too large. Max size is 5MB." To swap or remove it, tap Change cover on the photo, then Replace or Delete. Collections take a cover the same way.
How do I delete a list?
Tap Delete this wishlist in List settings and confirm. There's no undo: the list, its wishes and any reservations are gone for everyone, including people helping you run it.
Open the list and tap the sliders icon.
Tap Delete this wishlist at the bottom of List settings.
Check the name and number of wishes in "Delete this wishlist?", then tap Delete wishlist.
For a collection, tap Delete this collection in its settings, then Delete.
Tips
Might want it again next year? Set it to Only me instead of deleting, then switch it back when you need it.
No photo of your own? Find a photo has free ones: try a mood like Cozy or Ocean.
Use the description for what goes for every wish, like "second-hand is welcome".